A method in general practice of producing a metal tubular member formed of a thin metal sheet is to pressure-fit into an opening of a tubular body an end plate (lid) for blocking the opening to form superposed sections of the tubular body and the end plate and to integrally join the superposed sections by welding.
In forming such superposed sections, the following method is known as a method of fastening the superposed sections for instance.
There is a method by which, as shown in FIG. 18A, the inside diameter D10 of an opening section 102 of a tubular body 101 is set somewhat smaller than the outside diameter D11 of an end plate 103 and, as shown in FIG. 18B, the end plate 103 is pressure-fitted into the opening section 102 and joined by welding 104 (see Patent Document 1). This will be referred to as the first prior art.
There is another method by which in a muffler for vehicles, as shown in FIG. 19, thin sheet-made end plates 202 are pressure-fitted into both ends of a tubular body 201, the whole circumference of these superposed sections is fixed by laser welding 203 (see Patent Document 2). This will be referred to as the second prior art.
Further, there is still another method by which, as shown in FIG. 20A, first the inside diameter of an opening section 302 of a tubular body 301 is set greater than the inside diameter of general parts; an end plate (metal ring) 303 is loosely inserted into the opening section 302; then, as shown in FIG. 20B, the opening section 302 of the tubular body 301 is passed through a die under pressure to compress the diameter of the opening section 302 to bring the opening section 302 and the end plate 303 into tight contact; and then the contact sections are subjected to laser welding 304 (see Patent Document 3). This will be referred to as the third prior art.
Patent Document 1: JP-U-59-192661
Patent Document 2: JP-A-10-24381
Patent Document 3: JP-A-3-84850